This invention relates to towing vehicles and more particularly to means for locking the arm supporting the wheel engaging blade which support the rear portion of the tires of a vehicle to be lifted and towed by wheel lift apparatus.
Because of the large amount of plastic material used on the front and rear portions and bumpers of recent model automobiles, developments in the art of lifting and towing disabled vehicles by a towing vehicle have been directed toward what is known in the art as "wheel lift" devices, which engage and lift the front or rear tires of a disabled vehicle. Examples of towing apparatus incorporating such devices are illustrated in Wagner U.S. Pat. No. 3,182,829; Bubik U.S. Pat. No. 3,897,879; Cannon et al U.S. Pat. No. 4,451,193; Brown U.S. Pat. No. 4,473,334; Porter et al U.S. Pat. No. 4,573,857; Hamman U.S. Pat. No. 4,634,337; Bubik U.S. Pat. No. 4,637,623 and Holmes U.S. Pat. No. 4,679,978. As disclosed in each of these patents the tires of a disabled vehicle are disposed within the well of some form of cradle, the cradle having members which engage and support the front and rear of the tires carried therein.
The wheel supporting cradles generally have a fork of a substantially U-shaped configuration in plan, the legs of the cradle opening either inwardly, outwardly or rearwardly. In the later instance the open position is closed by a retaining member subsequent to the tire being disposed within the well, the retaining member engaging the rear of the tire. In the former cases, the rear of the tire is engaged by an arm, commonly known in the art as an "L" arm since it has that configuration, and such arm may have an upstanding arcuate contour conforming somewhat to the shape of the tire so as to provide greater support by the larger surface contact with the tire. Examples of the former "L" arm configurations are illustrated in at least the aforesaid Porter et al and Holmes patent, while examples of the latter "L" arm configurations are illustrated in at least Wagner and the Bubik '623 patents.
When a disabled vehicle is being towed, it is highly desirable that the tires rest securely within the cradle so that the momentum of the disabled vehicle does not result in the tires rolling and disengaging from the cradle when the towing vehicle accelerates or stops. On acceleration, the disabled vehicle and the tires tend to surge rearwardly, but upon stopping of the towing vehicle, the disabled vehicle and the tires tend to surge forwardly. Accordingly, it is highly desirable to have enlarged wheel engaging feet at the front and rear of the cradle.
In copending U.S. patent application Ser. No. 07/183,044 filed on Apr. 18, 1988, by Walter G. Lock and assigned to Holmes International Inc., the same assignee of the present application, there is disclosed a pivotably foldable ramp juxtaposed adjacent to the fixed ramp at the front of the cradle, the foldable ramp providing an extension of the fixed ramp, and thus an enlarged foot at the front, when in an operative position, yet may be pivotably folded to an inoperative position which permits the support member on which it is mounted to enter beneath low ground clearance vehicles without presenting an obstacle thereto.
However, as aforesaid, it is also desirable to have an enlarged foot for supporting the rear surface of the wheel or tire of the vehicle to be towed. Although the Bubik '623 patent does disclose an enlarged upstanding foot or blade, it requires that the arm to which the foot is attached be rotated a substantial amount for the foot to be received behind the rear of the tire, and it must then be lifted in order to adjust the arm longitudinally to engage the rear surface of the tire with the blade. When positioning the support arm it is more natural to merely slide the arm forwardly to engage the blade against the rear surface of the wheel. However, with the small wheel well clearances of recent automobiles this cannot be accomplished with the prior art blades such as that illustrated in Bubik '623 since the blade provides an obstacle for substantial movement of the arm so that it must be rotated to position the blade to closely adjacent the rear surface of the wheel
A solution to these and additional difficulties are provided by the apparatus disclosed in copending U.S. patent application Ser. No. 07/194,855 filed on May 17, 1988 by Walter Lock and Vernon Moore, the latter being one of the coinventors herein, and assigned to Holmes International Inc., the same assignee as that of the present application. In that application there is provided means for supporting the rear surface of the tire including a bar secured to the elongated "L" arm and a foldable plate carried by the bar for moving between a substantially upright operative position and a lowered position for providing clearance for entry of the rear support member beneath the vehicle and behind the tire, and for providing other operational features. The elongated arm is telescopically adjustably carried in a receptacle secured to a support beam which also carries the front member of the cradle. Once the arm is adjustably positioned for lifting and towing, a pin is inserted through a hole in the top of the receptacle and through a selected one of a number of bores in the upper surface of the arm to thereby lock the arm to the support beam.
Difficulties are sometimes presented when manipulating the arm to an adjusted position for insertion of the locking pin through the receptacle and the arm. Additionally, since the pin is inserted vertically and extends through the bottom surface of the receptacle, if the tow bar or support beam is on an unlevel surface, it is sometimes difficult to remove the pin when required for subsequent operations.